"I never wanted to relinquish this role at the club but as my England commitments have grown it is impossible to do justice to both roles."
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Gooch, who will remain at Chelmsford as club ambassador, has overseen an upturn in England's Test batting performances, particularly those of Alastair Cook.
The 26-year-old scored 766 runs in England's Ashes series win in Australia last winter before hitting a memorable 294 against India at Edgbaston this summer
Jonathan Trott, Kevin Pietersen and Ian Bell have all showed progress under Gooch, each notching Test double-hundreds since his arrival on the scene.
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Head coach Paul Grayson said: "We want to thank Graham for his services with the coaching side of the team.
"He has been a massive support to both the playing squad and myself but we understand his England requirements he has.
"I am really excited to be working alongside Matt Walker as he has vast knowledge of the game and I know he is looking forward to this next chapter of his career."
